1. Field of the Invention
The present invention relates to a composition for a vibration damper, a process for the manufacture of the composition, and the vibration damper.
2. Description of the Related Art
To avoid a transmission of vibration from a vibration source to other portions, a method has been adopted wherein a vibration-insulating rubber or an air spring is interposed between contacting areas of the vibration source and another portion. Although the transmission of vibration can be prevented by this method, it cannot dampen the vibration per se of the vibration source.
Accordingly, a method has been adopted in which the vibration of a vibrating member is damped by bringing a vibration damper into close contact with the vibrating member. This method, in principle, utilizes the conversion heat at the glass transition point or melting point of a resin component constituting the vibration damper, whereby the vibration energy is converted to heat, and thus the vibration per se is damped.
As the material constituting the vibration damper, a polyamide resin, a polyvinyl chloride resin and an epoxy resin have been used, but a vibration damper prepared from a vibration damper-forming composition comprising a polyamide resin as the main component has poor water resistance, chemical resistance, and mechanical strength, and thus has a limited application, and a vibration damper composed mainly of the polyvinyl chloride resin is defective in that it is difficult to form a vibration damper having a complicated shape and the manufacturing cost is increased when various vibration dampers are prepared in small quantities.
In principle, a vibration damper composed mainly of epoxy resin has a good vibration-damping property, and when a vibration damper composed mainly of epoxy resin is prepared, a room temperature-curing composition is usually used.
Where a vibration damper is attached to the parts formed by mass production, such as automobile parts and electric parts, preferably a process capable of continuously attaching the vibration damper is used, such as a cast molding process, transfer molding process or press molding process.
The room temperature-curing epoxy resin composition usually used for a vibration damper is a two-liquid type composition comprising a main component and a curing agent, and when a vibration damper is formed by using the above-mentioned molding process, the main component must be pre-mixed with the curing agent, and thus the preparation process becomes complicated. Moreover, the pot life of the room temperature-curing composition for a vibration damper is generally short, after the main component is mixed with the curing agent, and therefore, all of the composition must be used in a short period of time. Accordingly, the above room temperature-curing epoxy resin composition is not suitable for a process for the continuous production of a vibration damper.
To overcome the defects of the above-mentioned two-liquid type composition for a vibration damper, a potential curing agent has been used as the curing agent, but when potential curing agents customarily used for epoxy resins are used for the production of a vibration damper, it is difficult to obtain vibration dampers having a satisfactory vibration-damping capability.